Milling machines

Stability of the motorized head

Milling machines are machine tools with a very solid structure, as they must absorb the strong vibrations generated by the motorized head which is used for complex processing phases such as borings, perforations, cuttings etc. of metal parts (or other material). The state-of-the-art milling machines are equipped with automatic systems for the tool replacement, in order to turn the whole production process into a completely automated procedure. The machine can also be defined as boring mill: it is a special milling machine capable to perform boring procedures thanks to the high level precision of the movement control and to the stability of the motorized head.

These machines must be able to move on the piece surface; such movement can occur
in two different ways:
■ Moving the workbench on two axes (X and Y) and in case lifting the motorized head along the axis Z (for machines with a small dimension)
■ Keeping the workbench in a fixed position and moving the head along three or more axes, (for machines with a large dimension, which are also called machining centers).

Operator footboard, tool blocking/unblocking, tool warehouse etc. are some of the several controls developed by employing Duplomatic hydraulic components.

It is currently in progress the balancing of the vertical head of a boring mill weighing about 5000 kilos with a fast moving speed of 20 m/min; its open circuit system employs a VPPL070-PCX variable displacement piston pump with a flow rate set at 80 l/min and a working pressure of about 180 bars.

The balancing valve, which allows the zero setting of the load without harmful overloads on the head electric motor, is a DZCE5G-210 proportional valve with integrated electronics mounted into a block suitably studied and positioned near the use points.

Such a solution allows to obtain a balancing error threshold equal to zero compared to an error percentage of ± 10% noted in case a solution with closed circuit accumulators is applied.

This system is much more flexible than the closed circuit with accumulators but it must be applied with considerable strokes and weights of the head.